I have been a development engineer on automotive powertrains for almost 25 years, over half of that being specifically on cooling systems. On everything I have ever dealt with from heavy-duty Diesel engines to GM and Ford products in my own garage, the temperature marked on a thermostat has always been the start-to-open temperature. It will be fully opened 10-15°F higher. There is of course hysteresis on the way back down, so it won't be fully closed again until 5-10°F below the nominal temperature. If yours is marked 180°F and is actually operating between 160 and 180°F, something seems wrong to me. Put the thermostat and a thermometer in a pan of water on your stove and observe the temperature as it warms up and note when the thermostat starts to open and is fully open if you are in doubt of how it works or whether it is working correctly. As for the 1/8" hole in the thermostat, it is to vent air during the initial fill and start-up. I have never previously seen one that just had a hole. They usually have a jiggle valve, which is either a ball bearing in a cage or a ball with a hook through the hole, so it will vent air but then be held closed by moving coolant.

If I remember right the reason for the little bypass is to keep coolant slightly circulating during warm up to make sure you don’t get any hot spots before the thermostat opens

I loved the bubbles refrence!

On large equipment, such as a dozer the fan can be reversed in the cooler months to blow heat from the engine bay through the radiator to keep engine temp optimal. But i doubt the little Kubota would produce enough heat in that large engine bay to do the job, so you might need to start over and install an engine from a Cat D11 😅 I enjoy your videos Jimbo ❤

Let help you with your Japanese and help the KZfaq interaction algorithm. It’s a kei car, but pronounced like “kay”. It means light in the context of light duty. The original meaning of the word is “light” in the context of “trifling”. Keep ‘em coming this series has been fun!

I don't understand why people would complain about putting a supercharger on a diesel engine, as if it wouldn't benefit from it. Boost is boost. It doesn't matter what it comes from (unless they're talking about parasitic drag). The old Detroit Diesel 2 stroke engines used roots type blowers for scavenging. They wouldn't work properly without them. I, for one, can't wait to see how the Kubota will work with one. Nice work Jimbo!! 👏

This is my favorite Sunday show.

I don't know about the rest of your viewers, but I thought this video was just as entertaining as any video you have ever posted. And I don't mean that in a backhanded compliment kind of way. It is nice to see more of the backstage things that mostly never get filmed. The whole process that you may not is entertaining enough to show, is just as fascinating as the "exciting stuff" to your loyal viewers. Please bundle up and don't freeze off any of the wobbly bits.

People forget that turbo charging is turbo-supercharging ( the original term ) Back in the 50s, Cummins had a supercharged 275-300 hp, 743 ci truck engine that was nicknamed " The Iron Lung "

Little hole (or jiggle pin) is also needed so that the coolant behind the thermostat is allowed to warm up and not become a cold pocket, or the thermostat will open late.

It's 60° outside, windows open, frying up bacon and eggs, and watching robot cantina. What a way to start a Sunday

You should try to find a higher temperature thermostat (probably a 200°) and leave the bypass open. The bypass does alot of helpful functions.

Jimbo out here teaching practical engine engineering and abusing it in the most impractical way. And I am here for it. Keep up the great work!

The hole is the thermostat is to circulate water past the wax bulb. Inevitably it will slow warm up in some circumstances, but it can also delay opening and possibly cause overheating because a parcel of cold water is sitting next to the bulb while the water in the cylinder head is too hot. If there's a hole in the thermostat then that cold water can't get stuck there - the idea being a compromise is better than a boiling.

I like the vinyl window shade idea. Hook up a driving motor to it and some kind of motor controller connected to a micro controller with a temperature sensor. But it could become quite a project by itself but this is your rodeo, I'm just a happy spectator. Keep up the videos, they are do informative and entertaining.

Supercharger and a turbocharger is actually more optimal for a small displacement diesel engine. But most of the people complaining about a turbo wouldn't know anything about compound charging. The smallest turbo you can put on this engine, is still technically too large. So the turbine side doesn't really get moving till your engine RPM is in the higher side of what the engine can manage. Not ideal for a diesel engine where you want air down low to produce clean torque. Supercharger feeding into the compressor side of the turbocharger is a sneaky way to deal with the issue. Since roots blowers produce air pressure, even at idle if running fast enough.

Youre gonna want to add some heat shielding or heat tape around the downpipe by the supercharger. While the engine doesnt get too hot, they are close enough that it could cause issues to the innards of the AMR500.

I got up on the wrong side of the bed this morning and grumbled my way around feeling bad… then I saw that there’s a new video from Robot Cantina and the day was saved! 😎👍🏼

I suggest installing a throttle plate on the inlet of the stupid charger. Your main FE disadvantage will be the constant boost (added load) even in light throttle scenarios. If the engine is always under significant load (even when cruising), then it won’t make a difference. But if you want to reduce boost, creating vacuum with a throttle plate will reduce power consumption of the supercharger when it’s not needed. Like when you plug your vacuum cleaner hose and it revs up due to lack of load. So operate your throttle plate based on EGT while cruising, either manually or by fancy Arduino trickery, based on load and EGT. I love the project!

Thermostat bypass hole ensures that the pressure in the cooling system is the same both sides of the thermostat, so that the pressure cap can do its job regulating the system pressure.

bubbles would love working in your shop. thanks for the content jimbo!

Excellent content! And yeah, I don't believe 75% of the viewers appreciate how much time is spent off camera to make quality content such as this. Love the window shade idea!

Some v-belts are not intended to have idlerpulleys pressure the back of the belt. I think it needs a reinforced belt.

If you have problems with the supercharger belt failing, it will be from running the V belt "backwards" over the idler pulley. Had a friend chase that problem for quite a while. Love the channel!

As a bunch of people have already commented the bypass hole also promotes some circulation so the heated coolant actually makes it to the thermostat but I thought it would be interesting to comment that on all the systems care have the thermostat is almost entirely unchanged from the beginning of their use till now with that tiny hole being among the most significant in their evolution and I think that is awesome. Try to think of ANYTHING else that has remained almost the same for that long, I personally can't but I don't claim to be an expert in everything either so I am sure there are others.

I personally prefer superchargers over turbochargers, so seeing you commit to a supercharger is amazing to me

I would have selected a tight fitting cotter pin to restrict the lion's share of the hole in the thermostat. This would still allow air to purge. Restricting coolant flow on the radiator return hose could also assist in warm up time.

Vacuum filling the cooling system is the way to go if you have high points that are tough to keep from getting air pockets.

On the topic is Super Charger Vs Turbo. It's great that you're experimenting with the super charge. For future content after it is running correctly with the belt driven super charger, suggest converting to an exhaust driver turbo charger to do back to back comparison. Then to go the extra mile, do a Lancia Delta style turbo and super charger! What could go wrong, it'll be fun :)

Best part of Sunday. I love this series. I have a dream of putting a D-series Kubota in a '32 Indian Four-esque frame and riding it around town with a tractor flap. If it weren't for you, there is ZERO chance I could experience something similar vicariously. 😂

Put the thermostat in a pot of water and bring it to a boil and measure the water temp and mark when the thermostat starts to open. It usually does right when its suppose too. Sometimes a lot later at first which makes it overheat at first.

I had this whole thermostat debate and education process when I put together an oil cooler kit for my Subaru. Old hot rider logic says you want the coolest thermostat possible, but in the real world it’s nice when you engine can get to operating temperature in the cold and for oil it’s nice for it to be able to get hot enough to burn off condensation and fuel dilution. Long story short I found a 200deg thermostat and wish I could have found a 220.

I've really enjoyed following your projects so far. I've become quite the Robot Cantina Groupie. I imagine closing up that huge hole next to the radiator would help the engine run warmer in your cold Kansas winters. Anxiously awaiting your next video.

Keep em coming Jimbo I look forward to it every Sunday.

Suggest to install a jiggle valve in the bypass hole. Every Toyota made in the last ~40 years has one. I've always understood it's purpose to be for bleeding. Story from when I was on the bench: Had a vehicle I was troubleshooting - temps would drop at idle, and while driving down long hills in the winter. That rubber seal around the periphery between the interface between the moving and stationary parts had a tiny chunk out of it. The missing chunk was maybe 2-3 times the size of the hole in your thermostat, and the impact it had was much larger than I ever would have guessed.

That Volvo was a 444, and I got to drive a '59 model in the late 1960s. Shift throw amazingly long. Thanks for the memory!

Get an electric cabin heater. The electric heaters draw front the engine will give you a load to help warm the engine.

One of My Fondest Memories after Graduating H.S. in 84 was Working @ a Large Third Generation Welding Repair & Fabrication Shop. They Worked on Everything from what came in the Door to Aerospace. One of There Long Time Customers Came in With His Logging Truck, With A V-12 Detroit Diesel two Stroke. Twin Turbo, Suppercharged Straight Stacks. He Stated There Was """ NO "" Faster Truck in the Mountains Than His. The Super Charger Gets That Load Moving and Spins that V-12 Up Then The Turbos Kick In, & Him, His Truck & His Load Are Gone !!! ( and It Souded Beautiful ) But Every Inch Under That Hood Was Used !!! Radiator, Motor, Firewall..... Nothing To Spair

After you are done with just supercharging, I would love to see that engine twincharged. Like maybe compound setup with turbo and supercharger

I really enjoy all your videos and while this one might not have had exciting 0-60 tests, but I really enjoy watching the behind the scenes too!

Diesel 2 stroke Detroits came supercharged from the factory decades ago and still have a die hard following. They put those motors in everything from big boats, tractors, generators, over the road vehicles, and beyond. As a diesel mechanic I love where this channel is going and for branching out from the normal. And yes I think the kubota will benefit from the AMR-500 even if it’s only 6-7psi especially intercooled.

We have a lift with one of these engines. The radiator is about the size of a motorcycle radiator. Keep up the great work.

Glad to see the extra engine being put to good use instead collecting dust in my garage.

Diesel Insight lives!!!!!! Insight mods ftw!

The hole in the thermostat is to keep the coolant circulating, this keeps the coolant at a more consistent temperature and is nessaryfor proper thermostat function. Get a higher temperature thermostat is the way to go or add thermostacly controlled louvers in front of the radiator. The "test" you did took longer because of the lack of that little coolant flow. You risk high temperature areas that can boil, causing a cavitation type situation.

Love the Vice grip garage sticker. I watch both you and Derrick religiously.

Can't wait to hear that supercharger doing it's thing

You’re going to need a wheelie bar on this thing by the time you’re done with it, which is pretty impressive considering the thing is FWD! Thanks as always Jimbo and the rest of the RC crew!

Another reason for the bypass would be to allow coolant from the engine to flow past the pellet instead of having to rely on convection inside the coolant jacket of the engine.

I love this build as much as the rear drive converted Lincoln with the V10 Ford 4-valve engine going into it that BIY is doing. Both of you are criminally underrated channels.

A good idea to get more efficiency from the supercharger, if you haven’t thought of this by yourself already, build yourself some custom flanges. The ones that are on it are quite restrictive. A KZfaqr by the name of “Joni” or maybe “JoniK” I cant quite remember made custom flanges and I believe he said he picked up like 0.2/0.3 bar. I don’t know what that is in psi, but it’s gotta be a few psi at least. Great video Jimbo! Keep it up!

I knew about the shutter system on modern cars (road debris killed it on my car so I also know how stupidly expensive they are), but that window shade approach is genius.

The bypass also helps evenly warm the whole cooling systems. Engines with a stat, minus a bypass, can have temperature surges, as it comes up to opening temp the stat then slams shut when the cold radiator coolant enters the block. The repeated thermal shock can crack stuff.

Back in the day them their 2 stock diesels used both turbo and stupidchargers. Keep up the good work.

Thanks for all the effort you put in for our entertainment. Keep on keeping on. These small engine projects are intriguing.

My daily driver is a VW with the 2.0 liter, twin turbo diesel. I have noticed something over the years..........on normal commute, which is mostly open road, it is worse on fuel economy in winter........until the engine fully warms up ( my winter mornings in Australia is about +5C to -2C ). This does not happen with my gasoline powered vehicles. Superchargers can actually still be good for fuel economy, compared to running a bigger engine. At one point in Australia GM/Holden sold the commodore 4 door sedan with two sports options.......the V8 5.0 (2 valve head) and the Supercharged Buick V6 3800 (2 valve head). The Supercharged V6 made the same power as the V8 but for less fuel consumption provided they had the same high flow exhaust. See, Holden knew how good the blown V6 was, so from factory they deliberately choked the exhaust system to get it below the output of the V8. However, the blown V6 3800 did have the sophistication of a blower bypass so when coasting, the blower did not draw power from the engine. So, if you can get the little diesel Kubota to run some boost, it should benefit from making the same power at fewer rpm. However, Roots blowers like the AMR series have poor efficiency at high boost levels....the air temp will rise drastically (reducing density and thus performance). You might want to consider an intercooler at boost above 12 psi, there are compressor efficiency maps for roots blowers.

Thanks for all your hard work Jimbo

I thought that you'd inserted a reference to Bubbles from TPB, but on my rewatch I realized that it was just a Samsquatch.

Love your work, Jimbo 👍

Thank you Jimbo for entertaining the masses

Very interesting as always, Jimbo!

It fits like a glove. Great work!

The bypass hole allows warmed coolant to reach the backside of the thermostat, which will open it faster because the whole thermostat is being warmed instead of just the front side.

Great work Jimbo!

Best content on KZfaq.

Great video, Jimbo

Always so much work and planning

Great Video Jimbo!

Its the little things makes me smile, great work 🤖🙂

Jimbo, another great video, thanks for sharing 👍.

This is such a cool experiment. I love it 👍

The bypass hole also allows coolant to circulate around the thermostat so that it can sense the temperature. About the running temperature... A very long time ago, I went on a training course at Shell. One of the things they taught us was that the cylinder wall temperature must be above 75°C (167F) to avoid the condensation of the sulphur in the fuel (sulphuric acid) which causes corrosion /wear. Also if it is too cold then the cylinder clearances will be incorrect = bad.

Love the Vice Grip badge.

Great video Jimbo

The tiny hole helps for keep same pressure on both sides before and after thermostat also helps for bleeding air from system and should be installed to the top

I very much enjoy your experiments. Mikel ❤

What happens without the bypass is the thermostat can stay closed even though the coolant in the block is hot. The coolant that is stopped in the water neck never gets hot enough to cause the thermostat to open. Having a tiny trickle of coolant makes sure there is some circulation. Its not a big deal on something like this kubota but on other engines with an isolated mounting location it can cause havok. The engine can also experience a cold water dump, its unlikely, but it stresses the gaskets.

I was waiting for this so much but never get notifications from this channel no more!

Yes, fantastic series, I’m a relatively new follower. Enjoy every update.

In the 1970's, the Canadian variant of the Toyota Corolla 1200cc variant (KE31) had a "venetian blind" kind of louvre in front of the radiator that you would close in winter, and open in summer. It block most of the radiator in order to keep the engine warm.

Ive followed for a little while and this stuff is neat. Honestly, i enjoy behind the scenes just as much as the rest. Seeing what goes in to a project makes it worth it.

As always, fantastic video!

I would love to see the supercharger slightly under driven and a larger turbo compounding into the supercharger. The larger turbo would provide an elevated "atmospheric pressure" for the supercharger, increasing its efficiency for a given pressure. Maybe that could be a logical step after the Stupicharger project is complete! Lol. Also, as I believe I had mentioned before, a realitively cheap turbo to get your hands on would be a GM8 turbo from a late model GM 6.5 turbo diesel. It's wastegate is operated backwards from most turbos for diesels in that is "normally open" by design and uses vaccum to hold it shut. Most guys just wire the wastegate shut, and that should be no problem for this little motor, since the 6.5 struggled to overspin the turbo without a lot of mods anyway 😂

In my part of Canada (about the lowest I see is -40C/F), we used to use the cardboard in front of the radiator trick quite a bit before electric fans became a thing. With electric fans the cardboard trick doesn't have as much of an effect on available heat in the cabin. For example in my 3L minivan, when the outside temperature gets below about -30 the engine just doesn't produce enough heat to warm up the interior space for a very long time. The engine is running efficiently enough that it just doesn't have enough waste heat. It warms up faster if you drive it like you stole it, something that works much better with small 4 cylinder engines that don't get you into speed violations as quickly. You can also try putting the cardboard directly up against the radiator, but if you do, cut about a 6 inch diameter hole in it centered around the fan. If you're wildly off-center, you can actually make the blades flutter and hit the radiator fins. Putting the cardboard up against the radiator allows more of the coolant to come up to temperature, in essence creating a larger volume of heated water. This helps keep the air out of the heater stay a little more constant, because the cabin heater can overcool the engine in low load situations and you get cold air out of your heater. One other thing that can help is to install a higher temperature thermostat, but I don't know how useful it would be in your climate. I'd be interested to see if the supercharger without the intercooler would help with cabin heat :). Thanks for posting the video! Interesting stuff!

Ah, now he remembers... Older tractors (my experience was with the two-cylinder John Deeres) did not have pressurized cooling systems, and came standard with a radiator shutter. This was prior to the general availability of ethylene glycol coolant ("Prestone" was the first) which, when mixed with water in a pressurized cooling system, allowed the system to safely operate at temperatures much higher than the boiling point of water, dramatically increasing its cooling capacity. You would typically start the motor with the shutters closed, especially on a cold day, and then put the tractor to work. As the motor heated up you would watch the temperature gauge, and as the needle climbed to operating temperature you would open the radiator shutter and use that to moderate the temperature of the water in the cooling system-sort of like a manual thermostat. So your radiator shutter is old-school-cool! I continue to look forward to the weekly progress of the only supercharged three-cylinder diesel Honda Insight in the known world.

Love the VGG sticker! Keep up the good work

Thanks for the update!

Looking forward to seeing the Diesel with the Supercharger in action. Thanks for the Videos, Jimbo.

love your channel Jimbo. I wish I had a workshop so I could also do all these fun "what if?" projects

Looking forward to seeing the little diesel supercharged

Hell yeah, can't wait until this little guy starts making some boost!

I really enjoy your videos. Your voice and personality really make the videos enjoyable. Better than anything on TV. !!!!🇺🇸👍🤪🍺

Love your videos. Keep up the R&D. Btw great reference to BUBBLES....🇨🇦

Amazing, too bad you can't take that beauty on the road yet. I bet those numbers are way better now. As always, can't wait for the next video.

Having worked at a Kubota dealership. The most important thing when filling the cooling system, is to fill from the thermostat hole until it's full, then install the thermostat. Then fill the radiator. A Kubota engine will not burp out the air bubbles if you do not do it this way.

Great video thanks for sharing

the only input i have is keep doing what your doing its perfect

always a pleasure. Here for the thumbs up.

Love your videos!❤ Keep them coming please! 😁

Well done Jimbo. Very interesting one is this. I like the supercharger feeding turbo idea!. Turn the boost up!! 😎